[dba-VB] SHA1 to compute a hash

Hi Stuart --

 <<<
 It looks as though you  created 6 million random strings and  four of them
turned out to be identical. 
>>>
No, all SHA1 strings are different - these are 64 bit hashes of that
strings, which have got some collisions.

Thank you.

--
Shamil
 
-----Original Message-----
From: dba-vb-bounces at databaseadvisors.com
[mailto:dba-vb-bounces at databaseadvisors.com] On Behalf Of Stuart McLachlan
Sent: 19 ????? 2011 ?. 16:20
To: Discussion concerning Visual Basic and related programming issues.
Subject: Re: [dba-VB] SHA1 to compute a hash

If he is compacting  a 160 bit hash to a 64 bit hash,  he is certainly
increasing the odds of a collision - but I suspect that even at 64 bits, the
chances of a collision would be very low.

But that does not appear to be what you are testing. It looks as though you
created 6 million random strings and  four of them turned out to be
identical.  Therefore also had the same 
SHA1 digest.   What happens if you try it again, making sure that all of
your strings are 
unique.  Alternatively, what do you get if you add some code to show the
pairs of strings. Are they different?


--
Stuart

On 19 Mar 2011 at 16:03, Shamil Salakhetdinov wrote:

> Hi Stuart and John,
> 
> <<<
> AFAIK, no one other than you has found any
> >>>
> Yes, I was also confused how it comes to get SHA1 hashes collisions 
> but then I have thought that John probably "compacts" SHA1 hashes into
> 8 bytes surrogate keys?
> 
> Here (P.S.) is a "quick&dirty" "brute force" test code - 4 collisions 
> for 6 millions cycles for 8 bytes keys.
> 
> Please correct me if you find some errors in my sample code
> 
> Thank you.
> 
> --
> Shamil
> 
<<< snip >>>